We propose to develop a more sensitive, specific serologic assay for detection of Lyme disease especially early disease. Lyme disease is the most common vector borne infectious disease in the United States and Europe and as such it is a significant public health concern. The disease affects multiple organ systems including musculoskeletal, skin and nervous system and is included in the differential diagnosis of multiple diseases. In the absence of erythema migrans, the classic skin lesion of early Lyme disease, the diagnosis is established by the detection of an antibody response to Borrelia burgdorferi in patients with objective findings suggestive of the disease. Prompt diagnosis is important because early treatment of Lyme disease limits or prevents serious damage to the systems affected. Current serodiagnostics lack sensitivity in early disease. There are a number of B. burgdorferi antigens recognized early in human infection such as FlaB, OspC, VlsE, BBK32 and DbpA. None of these antigens is adequate when used alone in serologic assays. However, in combination they could provide the basis for a much improved assay. Linear epitopes have been identified in key B. burgdorferi antigens such as the invariable region 6 (IR6) of VlsE, proving that peptides containing these epitopes can be used as diagnostic targets. In this Phase I STTR, we propose to analyze FlaB, several groups of OspC, BBK32 and DbpA to define additional antigenic linear epitopes. We will then make synthetic peptides and compare their serologic reactivity to the corresponding recombinant protein. The new immunodiagnostic peptides discovered will be added to an improved VlsE-IR6 peptide to develop new, more sensitive immunodiagnostic assays. In a subsequent Phase II proposal we plan to screen and optimize a combination of immunodiagnostic peptides and prepare for validation of new immunoassays in both ELISA and lateral flow formats. Ultimately, our goal is to replace today's assays with a new generation of multi-peptide based tests. Because of greater specificity and the improvement of sensitivity that we can achieve, this approach could lead to the development of a single tier assay to detect antibodies against any of the three pathogenic genospecies of B. burgdorferi in both early and late Lyme disease. [unreadable] [unreadable] Lyme disease, the most common vector borne infectious disease in the United States affects multiple organ systems. Although prompt diagnosis and treatment prevents or limits serious injury to the systems affected, current serodiagnostics for Lyme disease lack sensitivity in early disease and are not specific enough to be used alone. Our objective is to replace today's assays with a new multi-peptide test. Because of greater specificity and the improvement of sensitivity that we can achieve, this approach could lead to the development of a single tier assay to detect antibodies against any of the three pathogenic genospecies of B. burgdorferi in both early and late Lyme disease. [unreadable] [unreadable] [unreadable]